Around 90 per cent of people worldwide are right-handed. Scientists have spent decades trying to find out why. Researchers from Oxford University in the UK believe they have a possible answer. Their research suggests that the answer is because of two features of human evolution. The first is walking on two legs, and the other is the large size of the human brain. When humans first started walking on two legs, their hands were free to do things. Our large brain worked out many things to do with our hands like using tools. If most people used the same hand, using tools and working with others became easier. This became useful for things like hunting and cooking.

Scientists thought the key to finding the answer was why only humans are largely right-handed. Primates (monkeys and apes) use both hands equally. The researchers compared human behaviour and brain patterns with 41 species of monkeys and apes. The research findings showed that humans have longer legs compared to their arm length. Another reason is that the left side of the brain controls the right hand. It is also responsible for motor skills and coordination. A researcher said: "By looking across many primate species, we can begin to understand which aspects of handedness are ancient and shared, and which are uniquely human."